During the development of gas-condensate fields the necessity to determine a formation current condensate saturation arises because the boreholes' productivity at gas-condensate fields often sharply drops due to the condensate drop-out in the near-wellbore zone and partial locking of the gas influx into the borehole. Thus a formation fluid saturation in a near-wellbore zone may rise to 40-60% and the borehole productivity may reduce several-fold. The development of gas-condensate deposits at the pressure below the dew-point results in the condensation of liquid hydrocarbons in a productive formation. Near-wellbore zone' peculiar feature is the difference in compositions of the gas and liquid phases as well as a formation condensate saturation from the respective parameters in the remaining part of the formation. Below the dew-point the yield reduction rate experiences the influence of the so-called ‘condensate bank’—a zone around a wellbore with a significant condensate saturation; the condensate banks may have the radius of several dozens meters. Simultaneously the boreholes' productivity factor may be reduced by the factor 3-4.
Until now condensate-saturation in a near-wellbore zone was not determined using geophysical research methods. Attempts have been taken to determine condensate saturation in gas-condensate formations but all of them provided the determination of condensate saturation in the entire reservoir and did not enable the determination of condensate saturation in a near-wellbore zone. Thus, USSR Certificates of Authorship Nos. 1514918 and 1645484 describe methods to determine the saturation of a gas-condensate reservoir with liquid hydrocarbons providing the injection of an indicator soluble in liquid hydrocarbons and an indicator inert to the liquid hydrocarbons with a gas carrier into the reservoir via an injection well with the subsequent record of the time when the indicators appear in the operating borehole products.